Pharmacology of the red eye Flashcards
What do topical drugs (drops or ointments) need to be able to do to be effective in treatment of eye problems ?
Need to be able to penetrate the cornea
What type of drugs are able to penetrate the epithelium of the eye and why ?
- Lipid soluble drugs penetrate epithelium
- Because the epithelium is lipophilic/hydrophobic
What type of drugs are able to penetrate the stroma of the eye and why ?
Water soluble drugs because the stroma is hydrophilic/lipophobic
Due to the nature of the epithelium and stroma in the eye what is the requirement of steroids to therefore be able to act on the eye ?
They need to be both hydrophobic and hydrophilic capability
What can be done to make steroids both hydrophobic and hydrophilic ?
- Alcohol or acetate used to make them more hydrophobic
- Phosphate used to make them more hydrophilic
What is the use of benzylkonium ?
Substance which can be added to drugs to enhance corneal penetration
What eye problems are steroids used for ?
- Post-op cataracts
- Uveitis
- To prevent corneal graft rejection
What are the main local side effects of giving steroids that can occur in the eye ?
- Cataract
- Glaucoma
- Exacerbation of viral infection
What are some of the systemic side effects of steroid use ?
- Gastric ulceration
- Immunosuppression
- Osteoporosis
- Weight gain
- Diabetes
etc
What is the action of steroids ?
To suppress inflammation, allergy and immune responses
What are the different strengths of steroids ? (from lowest to strongest)
- FML
- Predsol
- Betamathasone
- Dexamethasone/ prednisolone
What are the main medications used in the treatment of gluacomas ?
- Prostaglandin analogs eg Latanoprost (‘Xalatan’).
- Beta blockers (timolol, betaxolol, levobunolol carteolol etc)
- Carbonic anhydrase inhibitors eg topical eg Dorzolamide (‘Trusopt’) or systemic – acetazolamide (Diamox)
- Alpha2 adrenergic agonist e.g. Brimonidine (‘Alphagan’).
- Parasympathomimetic - pilocarpine
- Combination - (dorzolamide and timolol - Cosopt ).
What is the action of prostoglandin analogues in the treatment of gluacomas ?
Increase uveoscleral outflow and subsequently reduce intra-ocular pressure
What is the action of beta-blockers in the treatment of glaucoma ?
Work by reducing the rate of production of aqueous humour
What is the action of alpha2 agonists in terms of the treatment of gluacomas ?
Thought to work by reducing aqueous humour formation and increasing uveoscleral outflow
What is the action of Carbonic anhydrase inhibitors in the treatment of gluacomas ?
Work by reducing aqueous humour production
What are the common side effects of prostaglandin analogues in treatment of gluacomas?
Can cause stinging, blurring, of the eye and can also change the colour of the eye and increase the length of eyelashes
What are some of the side effects of beta-blockers ?
Local side effects:
- Burning/itch
- Erythema
- Dry eyes
- Allergic reactions
Systemic side effects:
- Low BP
- Reduced libid
- Depression
What are some of the side effects of alpha2 agonists ?
- Dry mouth,
- GI disturbances
- Taste disturbances
- Upper respiratory symptoms
- Headache
- Drowsiness
- Dizziness
- Malaise
What are the contraindications to using beta-blockers?
- Patients with bradycardia, heart block, or uncontrolled heart failure
- Should not be used in patients with asthma or a history of obstructive airways disease due to risk of bronchospasm
What are the side effects of carobic anhydrase inhibitors ?
- GI disturbances
- Taste disturbances
- long list etc etc
How does local anaesthetic work in the eye ?
Blocks sodium channels which impedes nerve conduction
How do mydriatic drugs work and give an example of them
Work by inhibiting parasympathetic innervation to the eye
e.g. tropicamide, cyclopentolate
What are the 2 main side effects of mydriatic drugs ?
- Blurring
- AACG - acute-angle closure gluacoma
